Fusion system and method for fusing spinal bones

ABSTRACT

This invention relates to a spinal fusion system and method for use as a prosthetic implant. The system and method includes a housing dimensioned to be situated between adjacent spinal bones, such as adjacent vertebrae. The housing cooperates with the spinal bones to define a graft area for receiving graft material, which may be inserted anteriorly into the housing during a surgical operation such as a vertebrectomy or discectomy. A housing may have various features such as migration preventers to prevent the housing from migrating posteriorly towards a spinal column and can be used with a cover that permits the housing to “float” relative thereto. Screws are provided in one embodiment and are dimensioned or configured to lock against each other to retain the screws and, consequently, the cover in place.

RELATED APPLICATION DATA

This application is a continuation-in-part of Ser. No. 11/624,341 filedJan. 18, 2007, which is a division of U.S. patent application Ser. No.10/675,361, filed Sep. 30, 2003, now issued as U.S. Pat. No. 7,182,782,all of which are incorporated herein by reference and made a parthereof. This application is also a continuation of U.S. patentapplication Ser. No. 10/858,629, filed Jun. 2, 2004, which is acontinuation-in-part of U.S. patent application Ser. No. 10/675,361,filed Sep. 30, 2003, now issued as U.S. Pat. No. 7,182,782, all of whichare incorporated herein by reference and made a part hereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a veritable prosthetic system and device and amethod for implanting the device and, more particularly, to a spinalfusion system and method for fusing spinal bones.

2. Description of the Related Art

Many types of prosthetic devices have been proposed in the past. Forexample, U.S. Pat. No. 5,192,327 to Brantagan concerns a surgicalprosthetic modular implant used singularly or stacked together tosupport and fuse together adjacent vertebrae or to totally or partiallyreplace one or more vertebrae in a vertebral column. Other surgicalimplant devices and methods are shown in U.S. Pat. Nos. 5,192,327;5,261,911; 5,713,899; 5,776,196; 6,136,002; 6,159,245; 6,224,602;6,258,089; 6,261,586; 6,264,655; 6,306,136; 6,328,738 and 6,592,586.Some or all of these devices have improved the success rate and havesimplified the surgical techniques in inter-body veritable fusion.

Among some of the problems associated with the prior art devices is thatafter the device is inserted into a patient during a surgical procedure,there was a possibility of retropulsion of the inter-body device andgraft material into the spinal cord or other neurological element.

Another problem with the prior art devices is that grafting material,which was inserted into the devices during the surgical procedure, couldnot easily be inserted from an anterior direction.

Moreover, in some of the prior art devices, the cover, if any, wastypically fastened directly to the device and to spinal bones, whichprevented the cover from being capable of moving relative to the device.In addition, in devices that used a cover, the cover did not function toboth retain the grafting material in the device and simultaneously fixthe spinal bones relative to each other.

Another problem with prior art cage systems is that the screws orfasteners which secured the cover onto the cages sometimes had atendency to unscrew themselves which is undesirable because the graftmaterial may exit the cage or because the cage itself may move. Anotherproblem is that the screws may withdraw, causing injury to localstructures by the screws themselves.

What is needed, therefore, is a system and method, which facilitatesovercoming one or more of the aforementioned problems as well as otherproblems and to provide a device that has unique features that willfacilitate reducing the risk associated with neurological surgeries andadvance the present state of the art.

SUMMARY OF THE INVENTION

It is, therefore, one object of the invention to provide a spinal fusionsystem and method which utilizes a housing that can be inserted, butcomprises features which, for example, enables the device to floatrelative to a cover, facilitates retaining any graft material within thedevice, facilitates fixing a relative relation among or between spinalbones, facilitates providing a cover for covering one or multipledevices, and/or includes locking features that facilitates preventingthe screws which secure the cover to the spinal bones from theretracting.

Another object of one embodiment is to provide a plurality of screwsthat are capable of locking to facilitate preventing the fasteners tobecome unfastened or unscrewed.

Another object of the invention is to provide fasteners at least one ofwhich has an eccentric to facilitate locking against an adjacentfastener in order to retain the fasteners and the cover in a lockedposition.

In one aspect, this invention comprises an apparatus for surgical use inhumans, comprising a housing for insertion between vertebrae in a humanspine, a recess in the housing for receiving bone graft material, acover securable to at least one of the adjacent vertebrae and beingconfigured to block egress of the bone graft material from the recess,and the cover and the housing being slidably engaged one to the other.

In another aspect, the invention comprises a surgical implant,comprising a housing, a recess in the housing for receiving bone graftmaterial, the housing having an opening in a side thereof, the openingcommunicating with the recess and being configured for insertion of thebone graft material into the recess, a cover mechanically engaging thehousing so as to permit sliding relative movement therebetween, thecover being configured to retain the bone graft material within therecess.

In yet another aspect, the invention comprises a surgical implant foruse with human vertebrae, comprising: a generally U-shaped housingdefining an opening in an anterior side thereof, a recess in the housingcommunicating with the opening, the recess being configured forreceiving bone graft material, and a cover in locating and matingengagement with the housing, the cover being securable to at least oneof the adjacent vertebrae and configured to block egress of the bonegraft material from the recess.

In still another aspect, the invention comprises a surgical implant foruse with human vertebrae, comprising: a generally U-shaped housinghaving a plurality of closed sides and an open side defining an openingat an anterior of the housing, the housing being disposable betweenadjacent vertebrae, a recess in the housing communicating with theopening, the recess extending through superior and inferior portions ofthe housing and being configured for receiving bone graft materialtherein, a cover mechanically coupled with the housing so as to permitsliding relative movement therebetween, the cover being disposed overthe opening and configured to block egress of the bone graft materialfrom the recess with the cover being securable to at least one of theadjacent vertebrae, and screw-receiving apertures in the cover foraccommodating screws securing the cover to the at least one adjacentvertebrae.

In yet another aspect, the invention comprises a method for fusingspinal bones together, comprising the steps of: removing diseased orinjured spinal bones and/or vertebral disks, and situating a spinalimplant between remaining spinal bones, the spinal implant comprising ahousing, a recess in the housing having bone graft material therein anda cover secured to at least one of the remaining spinal bones, the coverblocking egress of the bone graft material from the recess and the coverand the housing being slidably engaged one to the other.

In still another aspect, the invention comprises a method for fusingspinal bones together, comprising the steps of: removing diseased orinjured spinal bones and/or vertebral disks, and situating a spinalimplant between remaining spinal bones, the spinal implant comprising agenerally U-shaped housing having an opening in an anterior sidethereof, a recess in the housing having bone graft material therein, anda cover secured to at least one of the remaining spinal bones, the coverblocking egress of the bone graft material from the recess and the coverand being in locating and mating engagement with the housing.

These and other objects and advantages of the invention will be apparentfrom the following description, the accompanying drawing and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial side view of a human spine illustrating anteriorlydiscs between various spinal bones;

FIG. 2 is a partial side view of the spinal column shown in FIG. 1illustrating several of the discs removed, for example, after surgicalprocedure;

FIG. 3 is a partial side view of the human spine with the housingsaccording to one embodiment of the invention situated therein;

FIG. 4 is a partial side view of the human spinal column illustratinggraft material being inserted anteriorly into the housing;

FIG. 5 is a partial exploded side view of the embodiment shown in FIG.1-4 illustrating a cover and a plurality of screws which will secure thecover to the spinal column;

FIG. 6 is a side view similar to FIG. 5 illustrating after the cover hasbeen mounted to the spinal column;

FIG. 7 is an exploded view of the device shown in FIG. 6, illustrating aplurality of housings and a single cover for use with covering theplurality of housings;

FIG. 8 is partial side view illustrating an elongated housing and coverused during a vertebrectomy procedure;

FIG. 9 is a partial side view of the spinal column illustrated in FIG. 8showing the elongated housing situated between adjacent spinal bones ina single cover to be affixed to those spinal bones;

FIG. 10 is an exploded view of the circle area shown in FIG. 8;

FIG. 11 is a exploded view of the elongated housing illustrated in FIGS.8 and 9 and the cover and screws associated therewith;

FIG. 12 is a partial fragmentary view of the cover and housing after thecover has been situated between a pair of rails associated with thehousing;

FIG. 13 illustrates a partial side view of an embodiment showing aplurality of housings of different sizes used with a single cover;

FIG. 14 is an exploded view of the housings and cover illustrated inFIG. 13;

FIG. 15 is a partial anterior side view a human spine illustrating thediscs between various spinal bones;

FIG. 16 is a partial anterior view of the spinal column shown in FIG. 1illustrating several of the discs removed, such as by surgicalprocedure;

FIG. 17 is a partial anterior view of the human spine with the housingsaccording to one embodiment of the invention situated therein;

FIG. 18 is a partial anterior view of the human spinal columnillustrating graft material being inserted anteriorly into the housing;

FIG. 19 is a partial exploded anterior view of the embodiment shown inFIG. 1-4 illustrating a cover and a plurality of screws for securing thecover to the spinal column;

FIG. 20 is a anterior view similar to FIG. 5 illustrating the covermounted to the spinal column;

FIG. 21 is a fragmentary view illustrating various features of thecover;

FIG. 22 is another fragmentary view of the cover after the screws aremounted and the locking mechanism retains the screws therein;

FIG. 23 is a fragmentary sectional view of the embodiment shown in FIG.22 illustrating various features of the locking mechanism;

FIG. 24 is a schematic view of a process or method in accordance with anembodiment of the invention;

FIG. 25 illustrates another embodiment of the invention withoutcrossbars or migration preventers;

FIG. 26 is a view of another embodiment of the invention showing thecrossbars integrally formed in the housing and without migrationpreventers;

FIG. 27 is a view illustrating a plurality of migration preventers,without any crossbars;

FIG. 28 is a view illustrating a housing with a plurality of projectionswhich cooperate with the cover to prevent the housing from migratinganteriorly;

FIG. 29 is another view of the housing illustrating a plurality ofremovable crossbars without any migration preventers;

FIG. 30 illustrates another embodiment of the invention, similar to thedevices illustrated earlier relative to FIG. 1-20 showing details of thecross bars and notches for receiving them;

FIG. 31 is a view of a housing having walls having recessed areas forreceiving the cover;

FIG. 32 is a view of another embodiment of the invention showing theplurality of fasteners or screws in an unlocked position;

FIG. 33 is a view of the fasteners or screws shown in FIG. 32 in alocked position;

FIG. 34 is a view taken along the line 34-34 in FIG. 32;

FIG. 35 is a view taken along the line 35-35 in FIG. 33; and

FIG. 36 is an exploded view of the other embodiment of the inventionwith the locking screws illustrated in FIGS. 32-35.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIG. 1, a partial side view of a patient or person P isshown having a spinal column S and a plurality of spinal bones, such asvertebrae, 10, 12, 14 and 16. Note that a disc, such as discs 18, 20 and22 in FIG. 1, is located between adjacent pairs of spinal bones (e.g.,between bones 10 and 12, 12 and 14, and 14 and 16). During a spinalfusion procedure, such as a discectomy, the discs 18, 20 and 22 may beremoved so that adjacent vertebrae may be fused together

FIG. 2 illustrates a fragmentary view of the spinal column S shown inFIG. 1, with the discs 18, 20 and 22 removed. It should also beunderstood that during another surgical procedure, such as avertebrectomy, it may be desired to remove part or all of one of thespinal bones 10-16, as illustrated in FIG. 13. In this type ofneurological procedure, it may also be desired to fuse adjacent spinalbones together for reasons that are conventionally known. This inventionprovides means for facilitating and performing such procedures. For easeof illustration, FIGS. 15-20 provide corresponding anterior views to theside views shown in FIGS. 1-6, respectively.

In the embodiment being described, a spinal fusion system 24 is providedfor use as a prosthetic implant during a neurological procedure such asthe aforementioned vertebrectomy or discectomy. In general, after thediscs 18, 20 and 22 (FIG. 1) are removed, as illustrated in FIG. 2, aplurality of receiving areas 26, 28 and 30 (FIGS. 2 and 17) are definedby the areas between the surfaces of adjacent spinal bones 10, 12, 14and 16. As illustrated in FIG. 2, the area 26 is bounded in part by thesurface 10 a of spinal bone 10 and surface 12 a of spinal bone 12.Likewise, area 28 is partially bounded by surface 12 b of spinal bone 12and surface 14 a of spinal bone 14, and area 30 is bounded by surface 14b of spinal bone 14 and surface 16 a of spinal bone 16.

As illustrated in FIGS. 3-7 and 11 and as will be described in moredetail later herein, the spinal fusion system 24 comprises a housing 32dimensioned to be situated or received between adjacent spinal bones,such as bones 10 and 12. A housing 32 is situated in each of theplurality of receiving areas 26, 28 and 30, as illustrated in FIGS. 3-4.Each housing 32 cooperates with adjacent spinal bones to define a graftarea, such as areas 34, 35 and 36 in the view illustrated in FIG. 17,for receiving graft material 38 (FIGS. 4 and 18). As illustrated inFIGS. 4 and 18, the graft material 38 is situated in the areas 34, 35and 36 after placement of the housing 32.

As illustrated in FIG. 11, the housing 32 is generally U-shaped asshown. In the embodiment being described, the housing 32 comprises awell 33 defining multiple sides and comprising a predetermined shapeselected to cause the graft material to be formed into a multi-sidedfused coupling between adjacent spinal bones, such as bones 10 and 12 inFIG. 3. Although not shown, the housing 32 could define a shape otherthan rectangular, such as semi-circular, oval or other suitable shape asmay be desired. Note that the housing 32 comprises a first wall 32 a, asecond wall 32 b and a third wall 32 c joining the first wall 32 a andthe second wall 32 b. One or more of the walls 32 a-32 c may comprise aplurality of holes or apertures 40 which facilitate the fusing process.The apertures 40 also permit visualization of graft material 38 onx-rays.

As mentioned later herein, the predetermined shape defined by the spinalfusion system 24 may provide a fused multi-sided plug of fusion material38 having a height H (FIGS. 14 and 16) of at least two millimeters, buttypically less than approximately 180 millimeters. This height H mayvary depending on the vertical size or height H (as viewed in FIG. 16)of the areas 26-30 to be filled. For example, in the area 26 illustratedin FIGS. 2, 14 and 16, the height H of the area 26 generally correspondsto a height H1 (FIG. 1) of a disc, such as disc 18. Thus, the fusionmaterial 38 (FIG. 18) would resultantly have a fused height H2 (FIG. 18)that generally corresponds to the height H (FIG. 16) and height H1 (FIG.1). If, for example, a housing 32 having a longer height is required,such as height H3 in FIG. 14 and height H4 in FIG. 13, such as in theevent of a vertebrectomy, then the fusion system 24 and housing 32 willdefine a height that generally corresponds to the dimension or height H(FIG. 9) to be traversed. Thus, it should be understood that thedimensions of the generally U-shaped housing 32 of the spinal fusionsystem 24 is selected depending on the size of the area 26-30 to befilled and the environment or application in which the spinal fusionsystem 24 is used. In general, the width and depth of the housing 32will be approximately 9-20 millimeters and 7-20 millimeters,respectively.

As illustrated in FIGS. 5-7, 11, 14 and 21-22, the spinal fusion system24 further comprises a cover 42 comprising a plurality of apertures 44that receive a plurality of screws 46, respectively, which are screweddirectly into the spinal bones 10 and 16, as illustrated, for example,in FIGS. 5-6.

As illustrated in FIG. 11, the housing 32 comprises a first rail,channel wall or wall portion 48 and a second rail, channel wall or wallportion 50 which cooperate to define a channel area 52 for receiving thecover 42. It should be understood that when the cover 42 is received inthe channel area 52, the sides 42 a and 42 b become associated with thesides 48 a and 50 a. It should be understood that the cover 42 is notpermanently secured to the housing 32 after it is received in channelarea 52. This feature permits the housing 32 to migrate or floatrelative to the cover 42 even after the cover 42 is fixed to one or moreof the spinal bones 10-16 as illustrated in FIGS. 6 and 20. Asillustrated in FIG. 23, the edges 42 a and 42 b of cover 42 and sides 48a and 50 a may be beveled and complementary to facilitate locating andmating engagement between the cover 42 and housing 32.

As illustrated in FIGS. 3-6 and 16-20, after the graft material 38 isplaced in the housing 32 and the graft areas 35-36 (FIG. 17) defined bythe housing 32 and adjacent spinal bones, then the cover 42 is situatedbetween the walls or rails 48 and 50, as illustrated in FIGS. 6 and 19.The screws 46 may then be used to secure the cover 42 to one or more ofthe spinal bones 10-16 as illustrated in FIGS. 6 and 20. It should beunderstood that a feature of the invention is that the cover 42facilitates aligning the housings 32 in a substantially co-lineal orrelatively aligned position relative to each other and to the spinalbones 10-16, as illustrated in FIGS. 6, 19 and 20. In the setting ofmultiple level discectomy, the floating cover 42 allows limited,controlled settling of the cages or housings 32 in the vertical planewith respect to the cover 42. As illustrated in FIGS. 6, 8, 10 and 20,the cover 42 also provides means for providing a mechanical fixation ofthe adjacent spinal bones 10-16 relative to each other. Thus, while thehousing 32 cooperates with adjacent spinal bones, such as spinal bones10 and 12, to define a graft receiving area 34, the cover ismulti-functional in that it not only covers the opening of any graftareas, such as area 34 (FIG. 17), but it also secures and retains thespinal bones 10-16 in a fixed spatial relationship relative to eachother and relative to the housings 32. It should also be understood thatthe cover 42 may be fixed to one or more of the spinal bones 10-16 asmay be desired to accomplish either of the aforementioned functions.

As illustrated in FIG. 11, note that the walls 48 and 50 further defineprojections 48 b, 48 c, 50 b and 50 c as shown. As illustrated in FIGS.3-6 and 17-20, the projections 48 b, 48 c, 50 b and 50 c provide aplurality of migration preventers for preventing the housing 32 frommigrating posteriorly in the direction of arrow A (FIG. 3) toward thespinal cord S or other neurological elements after the housing 32 issituated between the adjacent spinal bones 10-16 as illustrated.Further, the migration preventers 48 b, 48 c, 50 b and 50 c enable asurgeon to locate each housing 32 between adjacent spinal bones, such asspinal bones 10-16 in FIG. 1, and move the housing 32 in the directionof arrow A in FIG. 3 until the migration preventers 48 b, 48 c, 50 b and50 c engage the surface 10 a of spinal bone 10 and migration preventers48 b, 48 c, 50 b and 50 c engage the surface 12 a of spinal bone 12. Asillustrated in FIG. 3, after the housings 32 are situated between thespinal bones 10-16 as shown, the migration preventers 48 b, 48 c, 50 band 50 c facilitate preventing the wall 32 c from being over-inserted bythe surgeon or from being over-inserted to a point where it engages thespinal cord S or other neurological elements.

The spinal fusion system 24 further comprises at least one migrationstop or crossbar 60 as illustrated in FIGS. 11, 12, 29 and 30. Thecrossbar 60 may be either integrally formed in housing 32, as shown inFIG. 26, or separate as illustrated in FIGS. 7, 11, 12, 14, 29 and 30,for example. As illustrated in the exploded view in FIGS. 10 and 11, thesurface 60 a of crossbar 60 engages and cooperates with surface 42 c ofcover 42 to prevent anterior migration in the direction of arrow B).Thus, the spinal fusion system 24 of the embodiment being describedprovides means for preventing insertion of the housing 32 to a pointwhere it might engage the spinal cord S (FIG. 3) or other neurologicalelements, such as dura mater, thecal sac, and also means forfacilitating prevention of migration of the housing 32 in an anteriordirection or in the direction of arrow B in FIG. 10 after the housing 32is situated as described herein and the cover 42 is mounted to one ormore of the spinal bones 10-16.

It should be understood that a plurality of the migration stops or crossbars 60 may be used alone or in combination with the migrationpreventers 48 b, 48 c, 50 b and 50 c. It should be understood that thestops 60 could be detachable, as shown in FIG. 26, or they could beintegrally formed in housing 32 (as shown in FIG. 26). Also, these crossbars 60 may be removably received in the notched receiving areas 94(FIGS. 29-30). For example, in anatomy that provided limited space, thesurgeon may elect not to use a housing with cross bars 60 or use ahousing that does not have integrally formed cross bars.

The system 24 further comprises a system or means for preventingretraction or back out of the screws 46 after they are screwed into thespinal bones 10-16 in order to secure the cover 42 thereto. The spinalfusion system 24 of the present invention may be used with conventionalscrew lock devices or with a unique locking mechanism and system, whichwill now be described relative to FIGS. 21-23.

As illustrated in FIGS. 21-23, the spinal fusion system 24 and, moreparticularly, cover 42 may be provided with at least one or a pluralityof resilient detents 62 which are generally L-shaped as shown and areresilient so that they can move laterally in the direction of doublearrow C in FIGS. 21-22 towards and away from a home position (FIG. 21)to permit the screws 46 first received in the apertures 44, and, second,locked into the cover 42. Thereafter, the screws 46 may be screwed intoa spinal bone, such as spinal bone 10, and when a screw head 46 a of thescrew 46 engages a detent portion 62 a of the resilient detent 62, theresilient detent 62 moves in a direction away from the apertures 44until the screw head 46 a clears the portion 62 a. After a top surface46 b of the screw head 46 a has cleared the bottom surface 62 a 1 (asviewed in FIG. 23) of portion 62 a, the resilient detent 62 moves backtoward aperture 44 to the home position until the portion 62 a andsurface 62 a 1 are operatively positioned over surface 46 b of screw 46,thereby retaining and preventing the screws 46 from backing out of thecover 42 and thereby preventing the screws 46 from backing out of thespinal bone 10.

The plate comprises a first surface 50 d (FIG. 23) and a second surface50 e. The plate member further comprises a seat or edge 50 f (FIG. 21)associated with the first surface 50 d and the detent 62 a associatedwith the second surface 50 e.

In the embodiment being described, the components of the spinal fusionsystem 24, such as the housing 32, first channel wall portion 48 andsecond channel wall portion 50, crossbar 60, cover 42 and screws 46 maybe made of any desired composition or material such as a polymer,composite polymer, titanium, stainless steel, carbon fiber or othersuitable material.

A method for fusing spinal bones together will now be described relativeto FIG. 22. It should be understood that this procedure may be usedduring a vertebrectomy or discectomy or other neurological procedureduring which it is desired to fuse spinal bones together. For ease ofillustration, the embodiment will be described as used during adiscectomy procedure during which the discs 18-22 (FIG. 1) are removedso that spinal bones 10-16 may be fused together. The procedure beginsby situating a patient P on an operating table (not shown) and providingan appropriate incision as conventionally known to expose the spinalbones such as the bones 10-16 illustrated in the side view shown in FIG.1 and in the anterior view illustrated in FIG. 15. (Block 70 in FIG.22). At Block 72, the vertebrae or discs, such as discs 18-22 in FIGS. 1and 15, are surgically removed revealing the areas 26-30 in FIGS. 2 and16. At Block 74, the housings 32 are inserted in the direction of arrowA (FIG. 3) into the areas 26, 28 and 30 until the migration preventers40 b, 48 c, 50 b and 50 c engage the surfaces of the spinal bones 10-16,such as the surfaces 10 a and 12 a illustrated in FIG. 3. (Block 74 inFIG. 22). As mentioned earlier herein, the migration preventersfacilitate preventing inserting the housing 32 to a point which wouldcause the wall 32 c to engage the spinal column S.

As illustrated in FIGS. 3 and 17, the housing 32 cooperates withadjacent spinal bones, such as bones 10 and 12 to define the graftreceiving area or cavity 34 in which the graft material 38 (FIG. 4) maybe inserted. As mentioned earlier herein, these graft areas 34-36 maycomprise a shape which is generally rectangular, as defined by the shapeof the housing 32, but it could comprise another shape by simplyproviding a housing 32 having a different predetermined shape. Thus, thehousing 32 may be provided in a circular or arcuate shape in which casethe graft area 34 would define a generally circular or arcuate area,which would cause the graft material to form a similar shape. Othercurved or multi-sided shapes may be defined by providing anappropriately or correspondingly shaped housing 32, depending on theselected or desired shape that the physician would like the fused graftmaterial 38 to assume after it has fused to the adjacent spinal bones.

At Block 76, the graft material 38 is inserted and at Block 78, thecover 42 is situated in the slot or area 52 defined by the walls 48 and50. As mentioned earlier herein, the cover 42 facilitates covering theopenings, such as openings 34 a and 36 a of the graft areas 34 and 36,respectively. The surgeon secures the cover 42 to one or more of thebones, as illustrated in FIGS. 5-6 and 19-20 and then closes the patient(Block 80).

Again, and as mentioned earlier, a feature of the invention is that itprovides a fixing system for fixing the location of the bones 12-16relative to each other. Simultaneously, the system 24 permits thehousing 32 to “float” between adjacent bones, such as bones 10 and 12 inFIGS. 3 and 6. This is advantageous for reasons mentioned earlierherein. Another advantage on this feature of the invention is that if itis necessary to operate on the same patient at a later time (Block 82 inFIG. 24) and, for example, add one or more housings 32 in order to fuseother spinal bones together, then the cover 42 can simply be removed ata later time, another discectomy or vertebrectomy performed and anotherhousing 32 inserted. Another cover 42, or perhaps a second cover maythen be used to seal the additional housing 32 after it is situated inthe manner described herein. Thus, this invention provides a system andmethod, which is flexible and will permit the addition or insertion ofadditional housings 32 of the same or different sizes during a secondoperating procedure as illustrated in Block 82.

FIGS. 1-8 and 15-20 illustrate the general procedure and use of theinvention in an illustrative discectomy wherein three discs are removed,replaced with housing 32, and graft material 38 inserted as described,and cover 42 situated and mounted as described herein. In theillustration shown in FIGS. 1-8 and 15-20, three discs 18-22 are removedand the spinal bones 12-16 are fused together using the system andmethod as shown and described. It should be appreciated, however, thatthis system and method may be used with fewer or more housings 32 andwith one or a plurality of covers 42 as may be desired or required. Forexample, if only one of the discs 18-22 needed to be excised and onlytwo of the spinal bones 10-16 fused together, then only one housing 32and cover 42 may be necessary. Likewise, as mentioned earlier herein,the housings 32 may comprise a different dimension or different height H(FIG. 14) to span a greater area, such as the area H4 illustrated inFIGS. 13 and 14. For example, FIGS. 13 and 14 illustrate a vertebrectomywherein the spinal bone 12 has been removed along with the disc betweenspinal bones 14 and 16. This provides areas 80 and 81 in which anelongated housing 32′, such as the housing 32′ illustrated in FIG. 14may be inserted. After the housings 32 and 32′ are inserted between thespinal bones 10-14 and 14-16 as shown in FIG. 13, graft areas 82 and 84are provided for receiving the graft material 38. As illustrated in FIG.13, the cover 42 would have a corresponding elongated shape for fixingthe bones 10 and 14 together and for covering both openings 82 and 84 orhousings 32 and 32′.

It is also anticipated that the invention may be used in a multitude ofprocedures, such as a vertebrectomy (FIGS. 8 and 9), discectomy (FIGS.1-7, 13-20, or even a combination of a vertebrectomy and discectomy asillustrated in FIGS. 13-14. As mentioned and described earlier herein, acombination of different sizes of housings 32 and covers 42 may be usedas shown. Although it is preferred that a single cover 42 be used, itmay be desired in some applications to use multiple covers 42, such aswhere the removed discs are not adjacent.

In the illustrations being described, the housings 32 comprise thecrossbar 60 which cooperate with the cover 42 to prevent anteriormigration of the housing after the screws 46 are secured to the spinalbones as illustrated in FIGS. 6, 9 and 13.

FIGS. 25-30 illustrate other embodiments of the invention. In FIG. 25, agenerally U-shaped housing 32 is provided without the walls 48 and 50 orcrossbar 60. This embodiment may be useful. This may be useful if itwere desired to insert housing 32 in local anatomy so that it could beloaded from the side or laterally, rather than anteriorly, as previouslydescribed.

In FIG. 26 a housing 32′″ is provided with the crossbars 60, but withoutthe walls 48 and 50. In this embodiment it may be useful to use such ahousing design when the local anatomy provides limited space.

FIG. 27 illustrates yet another embodiment of the invention illustratinga housing 32 that is provided with a plurality of protrusion 86, 88, 90and 92 that do not span completely between the walls 32 b or 32 atogether but yet provide the protrusions 86-92 which will engage thecover 42 if the housing attempts to migrate anteriorly as describedearlier herein. FIGS. 1-24, 29 and 30 show embodiments of the inventionwhere the crossbars 60 are not integrally formed with the housing 32,but received in the notched areas 94 as shown. As mentioned earlier, thecrossbars 60 may be separate or may be integrally provided with thehousing 32. Providing detachable crossbars 60, such as is shown in theembodiments illustrated in FIGS. 25, 28 and 29, enable the walls 32 aand 32 b to flex towards and away from each other. The housing 32 may beprovided with a malleable material in which case the surgeon can changethe general U-shape of the housing 32 to accommodate the size or shapeof the areas 34 and 36 (FIG. 17). In the embodiment described, housing32 and cover 42 may be made of titanium, polymer or a bioresorbablematerial.

FIG. 31 illustrates the walls 48 and 50 having notched areas 49 and 51for receiving the cover 42 which is dimensioned to fit, therebyeliminating the need for cross bars 60.

FIGS. 32-36 illustrate another embodiment of the invention. In thisembodiment, those parts that are the same or similar to the partsillustrated in FIGS. 1-30 are identified with the same part number,except that the parts in FIGS. 31-36 have an apostrophe (“'37 ) markadded thereto.

In this embodiment, the cage system 24 comprises a cover 400 forsituating in the channel area 52 (FIG. 11) to facilitate preventinginterior migration of the graft material 38. In order to secure thecover 400 over the graft area 34 or 36, a locking system, means andmethod are provided for retaining the cover 400 on the housing 32. Inthe embodiment being described, the locking system 402 comprises aplurality of screws, fastening means or fasteners 404, 406, 408 and 410that are received in openings, such as openings 405 in the cover plate400 as shown. Note that the fasteners 404-410 comprise a plurality offemale openings or slots 404 a, 406 a, 408 a and 410 a for receiving atool, such as a hex wrench for tightening and loosening the fasteners404-410.

In the embodiment being described, the fasteners 404 and 408 comprise ahead 404 b and 408 b that have a planar or flat portion 404 b 1 and 408b 1 as shown. As best illustrated in FIGS. 34 and 35, note that thefasteners 408 and 410 each comprise threads or a threaded portion, suchas threads or portions 408 c and 410 c of fasteners 408 and 410,respectively. Note that a distance or small radius D1 between center C1and flat portion 408 b 1 in FIG. 34 is smaller than the distance orlarge radius D2 measured by the distance between center C1 and wall 408b 2 in FIG. 35. The difference in the distances D1 and D2 facilitatesdefining a cam surface or lobe on the wall 408 b 2 whose use and purposewill be defined later herein.

In the embodiment being described, one or more of the heads 404 b, 406b, 408 b and 410 b may comprise an indicia, such as a grind mark orother indicator 412 and 414 (FIG. 32), to facilitate and assist a user,such as a doctor, to identify the small radius portion D1 during asurgical procedure. Thus, the indicia 412 and 414 facilitate definingthe surface associated with the flat portion, such as portion 404 b 1.

It should be understood that when the pairs of fasteners 404-406 and408-410 are aligned such that the flat portion 404 b 1 and 408 b 1 andshort or small radius portion D1 are situated in opposite or closest towall 406 b of screw 406 and wall 410 b of screw 410 the adjacentfasteners 406 and 410 respectively, may be rotated and screwed into, forexample, vertebrae 10, which will secure and retain the cover 400 overthe graft area 34 or 36. Although not shown, the locking system of thepresent invention may comprise eccentric fasteners of screws havingeccentric heads (i.e. where a head center is offset from a thread axis)and fasteners that are used with non-eccentric fasteners. For example,and as illustrated in FIG. 33, fasteners 404 and 408 may comprise theaforementioned eccentric, while adjacent fasteners 406 and 410,respectively, may be non-eccentric fasteners or screws.

In any event, the small radius portion D1 permits the adjacent fasteneror screw such as screw 410, whether it has an eccentric or not, to beturned when the small radius portion D1 or flat portion 408 b 1 issituated in opposed relationship to the adjacent screw (as illustratedin FIGS. 32 and 34). For example, FIG. 34 illustrates that when thefasteners are aligned such that the indicia 414 are aligned asillustrated in FIG. 32, a gap G exists between the portions 408 d 1 andwall 410 d of screw 410 as shown. The gap G permits either or both ofthe fasteners 408 and 410 to rotate in either a counter-clockwise orclockwise direction during fastening and unfastening of the fasteners tothe vertebrae as described earlier herein with the prior embodiments.

When it is desired to secure the cover 400 over the housing 32, thefasteners 404-408 are placed in the cover and aligned as illustrated inFIG. 32. The fasteners 404-408 are rotated and screwed into vertebrae 10in a clockwise direction until it is seated. These fasteners 404 and 408are then “backed out” less than a full turn until flat surface 404 b 1and 408 b 1 are aligned as shown in FIG. 32. The surgeon may use theindicator 412 and 414 to perform this alignment. This alignment presentsthe gap G (FIG. 34), which permits the fastener 410 to be rotated in aclockwise direction until completely screwed into vertebrae 10.

Next, the adjacent fastener (406 for the 404-406 pair and 410 for the408-410 pair) is inserted into opening 405 in cover 400 and in FIGS. 32and 34 until they are fully seated into the vertebrae 10. For example,in the illustration shown in FIGS. 32 and 34, the fastener 408 isrotated in a clockwise direction with a tool, such a hex wrench (notshown) until it is fully seated into the vertebrae 10.

The fastener 408 is again rotated in the clockwise direction (as viewed)until the large radius portion D2 and the wall portion 408 b 2 engagesand comes against the wall 410 b of the fastener 410.

It should be appreciated that when the fasteners 404-410 are secured inthe locked position in the manner described, they facilitate retainingthemselves in the locked position. For example, if fastener 410 beginsto rotate in a counterclockwise direction (as viewed in FIG. 33) it willcause fastener 408 to rotate in a clockwise direction which, in turn,causes fastener 408 to tighten and resist the counterclockwise rotationof fastener 410. If fastener 410 would rotate, fastener 408 would screwdeeper into the vertebrae 10.

FIG. 36 is an illustration similar to FIG. 11 showing the orientationand alignment of the cover 400 and fasteners 404-410 to the housing 32.

Advantageously, the various embodiments of the invention illustrated inFIGS. 1, provide a system and method for inserting graft material 38into a graft area 34 and 36 (FIG. 17) to fuse a plurality of bones suchas bones 10-18 together. The system and method also provide means forfixing the bones 10-18 relative to each other, while permitting thehousing 32 to cooperate with adjacent bones 10-18 to define a graft area34 and 36 (FIG. 17) and to also float relative to the cover 42. Thelocking system illustrated in FIGS. 21-23 further facilitates providinga locking system that does not require the use of any tools, yetprevents back out of the screws 46.

While the apparatus and method described constitute preferredembodiments of this invention, it is to be understood that the inventionis not limited to this precise apparatus and method, and that changesmay be made in either without departing from the scope of the invention,which is defined in the appended claims.

1. An apparatus for surgical use in humans, comprising: a housing forinsertion between vertebrae in a human spine; a recess in said housingfor receiving bone graft material; a cover securable to at least one ofthe adjacent vertebrae and being configured to block egress of the bonegraft material from said recess; and said cover and said housing beingslidably engaged one to the other.
 2. The apparatus of claim 1 whereinsaid housing is generally U-shaped.
 3. The apparatus of claim 2 whereinsaid housing comprises a plurality of closed sides and an open sidecommunicating with said recess.
 4. The apparatus of claim 3 wherein saidopen side is located at an anterior of said housing.
 5. The apparatus ofclaim 3 wherein one or more of said closed sides includes a plurality ofapertures formed therethrough.
 6. The apparatus of claim 1 wherein saidcover is securable to each of the adjacent vertebrae.
 7. The apparatusof claim 1 wherein said cover is configured to block egress of saidhousing from between the adjacent vertebrae.
 8. The apparatus of claim 1wherein said cover includes screw-receiving apertures for accommodatingscrews securing said cover to the at least one adjacent vertebrae. 9.The apparatus of claim 8 further comprising screws disposed in saidapertures.
 10. The apparatus of claim 1 further comprising bone graftmaterial in said recess.
 11. A surgical implant, comprising: a housing;a recess in said housing for receiving bone graft material; said housinghaving an opening in a side thereof, said opening communicating withsaid recess and being configured for insertion of the bone graftmaterial into said recess; a cover mechanically engaging said housing soas to permit sliding relative movement therebetween, said cover beingconfigured to retain the bone graft material within said recess.
 12. Thesurgical implant of claim 11 wherein said housing is generally U-shaped.13. The surgical implant of claim 11 wherein said housing is usable asan intervertebral implant and disposable between adjacent vertebrae,said cover being securable to at least one of the adjacent vertebrae.14. The surgical implant of claim 13 wherein said cover is securable toeach of the adjacent vertebrae.
 15. The surgical implant of claim 11wherein said cover is disposed over said opening and is moveableindependently of said housing.
 16. The surgical implant of claim 13wherein said cover includes screw-receiving apertures for accommodatingscrews securing said cover to the at least one adjacent vertebrae. 17.The surgical implant of claim 16 further comprising screws disposed insaid apertures.
 18. The surgical implant of claim 11 further comprisingbone graft material in said recess.
 19. A surgical implant for use withhuman vertebrae, comprising: a generally U-shaped housing defining anopening in an anterior side thereof; a recess in said housingcommunicating with said opening, said recess being configured forreceiving bone graft material; and a cover in locating and matingengagement with said housing, said cover being securable to at least oneof the adjacent vertebrae and configured to block egress of the bonegraft material from said recess.
 20. The surgical implant of claim 19wherein said cover is securable to each of the adjacent vertebrae. 21.The surgical implant of claim 19 wherein said cover is disposed oversaid opening and is moveable independently of said housing.
 22. Thesurgical implant of claim 19 wherein said cover includes screw-receivingapertures for accommodating screws securing said cover to the at leastone adjacent vertebrae.
 23. The surgical implant of claim 22 furthercomprising screws disposed in said apertures.
 24. The surgical implantof claim 19 further comprising bone graft material in said recess.
 25. Asurgical implant for use with human vertebrae, comprising: a generallyU-shaped housing having a plurality of closed sides and an open sidedefining an opening at an anterior of said housing, said housing beingdisposable between adjacent vertebrae; a recess in said housingcommunicating with said opening, said recess extending through superiorand inferior portions of said housing and being configured for receivingbone graft material therein; a cover mechanically coupled with saidhousing so as to permit sliding relative movement therebetween, saidcover being disposed over said opening and configured to block egress ofthe bone graft material from said recess with said cover being securableto at least one of the adjacent vertebrae; and screw-receiving aperturesin said cover for accommodating screws securing said cover to the atleast one adjacent vertebrae.
 26. A method for fusing spinal bonestogether, comprising the steps of: removing diseased or injured spinalbones and/or vertebral disks; and situating a spinal implant betweenremaining spinal bones, the spinal implant comprising a housing, arecess in the housing having bone graft material therein and a coversecured to at least one of the remaining spinal bones, the coverblocking egress of the bone graft material from the recess and the coverand the housing being slidably engaged one to the other.
 27. The methodof claim 26, further comprising the step of: blocking egress of thehousing from between the remaining spinal bones with the cover.
 28. Amethod for fusing spinal bones together, comprising the steps of:removing diseased or injured spinal bones and/or vertebral disks; andsituating a spinal implant between remaining spinal bones, the spinalimplant comprising a generally U-shaped housing having an opening in ananterior side thereof, a recess in the housing having bone graftmaterial therein, and a cover secured to at least one of the remainingspinal bones, the cover blocking egress of the bone graft material fromthe recess and the cover and being in locating and mating engagementwith the housing.
 29. The method of claim 28, further comprising thestep of: blocking egress of the housing from between the remainingspinal bones with the cover.